In this article, we investigate the loss of local ecological knowledge (LEK) of wild mammals among quilombolas in southeastern Brazil. Using an Event Ecology approach, free listing exercises, questionnaires, and semi-structured interviews, we recorded local knowledge relevant to wild mammals as well as key events in the life histories of residents. Next, we built a causal model connecting age; formal education; years outside the community; years in the pre-village context; and individuals' degree of LEK. Statistical analysis showed that the formation of sedentary communities and the abandonment of swidden cultivation among young people are the main sources of the erosion of LEK observed. This is the first study connecting a decrease in swidden cultivation with loss of local knowledge about fauna. The importance of swidden cultivation for non-agricultural domains of knowledge was somewhat surprising and particularly relevant in the current scenario of a worldwide collapse of this horticultural system.